Manganese alloy



Patented Sept. 6, 1938 MANGANESE ALLOY Anthony G. de Golyer, New York,N. Y.

No Drawing. Application October 21, 1936, Serial No. 106,805

1 Claim.

Thisinvention relates to a new alloy steel, and relates particularly toan alloy steel containing manganese and boron.

The object of this invention is to supply a manganese alloy steel whichdoes not require thermal treatment to render it commercially useful;which has materially greater resistance to abrasion; and impact than theheretofore known manganese steels; and, which may be readily repaired orrebuilt by welding with no adverse effects on the physical properties ofthe parent metal.

Cast manganese steel, containing from to 14% manganese and more than 1%carbon,

commonly termed Hadfield steel, has been extensively used for parts ofequipment subjected to wear by abrasion and impact. This type of steelis extremely brittle in the as cast condition owing to the presence of arelatively high percentage of free carbides of iron and manganese. Athermal treatment is necessary to change the structure of the steel, anddevelop the required tensile strength and toughness. Briefly, thistreatment comprises slowly heating the cast steel to a temperature ofapproximately 1850 degrees F., and maintaining it at such temperaturefor a protracted period of time to form a solid solution of themanganese and iron carbides in the iron matrix. When the steel isconverted to a substantially austenitic condition it is quenched inwater to prevent precipitation of manganese and iron carbides, whichoccurs when the steel cools at a normal rate.

Properly heat treated steel of this type is characterized. by fairlyhigh tensile strength,

e. g., 90,000 to 120,000 lbs. p. s. i., a low elastic limit, butconsiderable ductility and toughness, and low hardness, i. e., 180 to200 Brinell.

Repeated cold work on the surface of the heat treated steel eifects amaterial change of structure, apparently causing segregation of the hardand brittle manganese and iron carbides, with the result that thehardness'of such outer layer is increased to from 400 to 480 Brinell. Atthe point where the hardness approaches the above maximum, the outerlayer becomes so brittle that it flakes or chips off, exposing metal ofappreciably lower hardness.

The grade of ordinary manganese steel best adapted for use on wearingparts of equipment contains from 12% to 13.5% manganese and at leastone-tenth as much carbon; this ratio of carbon being required to give tothe steel the work hardening characteristic. Some forged manganesesteels contain slightly less than 1% carbon, and while a relatively hightensile strength and toughness can be developed in such steels they willnot resist abrasive wear to the same degree as the steels containing ahigher ratio of carbon. It has been determined that more than 2%manganese in steel acts to appreciably lower the carbon ratio of theeutectoid. Consequently, in all commercial manganese steel the carbon isabove the eutectoid ratio. When such steel is 10 heated to a temperatureof some 700 degrees F., or higher, and permitted to cool at a normalrate in air, the austenitic structure is destroyed, and the steel isembrittled. When ordinarymanganese steel is welded a portion of steeladjacent 15 to the weld is heated to a temperature suflicient- 1y highto result in reversion of the polyhedral structure to one approximatingthat of the Original casting. For this reason the Hadfield type of steelis not suitable for use as a weldrod, ex-

cept when the deposited metal 'and the embrittled parent metal can beproperly heated and quenched in water. The disadvantages of this inindustrial operations are obvious.

A steel containing from 2% to 10% nickel, i addition to the usualamounts of manganese and carbon, has been proposed in an attempt toovercome some of the difliculties of welding manganese steel. In thiscase nickel functions to fonn a more stable solid solution of iron andmanganese carbides in the iron matrix, and thus inhibit theprecipitation of free carbides when the steel is allowed to cool at anormal rate from elevated temperatures. It has been found, however, thatthe presence of an effective amount of nickel also acts to greatlyretard surface hardening of the steel under cold work. Consequently,manganese steel containing nickel does not resist abrasion as well asordinary manganese steel, and, for this reason industrial use of thenickel containing steel is restricted to weld rods.

I have discovered that an alloy containing manganese from approximately6.25% to 16%, boron 0.25% to 1.75%, carbon from approximately 0.10% tonot more than 0.85%, and the balance principally iron, has materiallyhigher hardness than previously known manganese steels, and that many ofthe other physical properties and characteristics are also superior.

One distinct advantage of the alloy of the prescut invention is that itmay be used for a wide variety of industrial purposes including wearingparts of equipment, in the as cas condition. The cast metal has aminimum hardness of about 525 Brinell, and this is increased from 1501;56

200 hardness numbers by cold work. The tensile strength, ductility andtoughness of the alloy are, in general, superior to similar propertiesof heat treated manganese steel of the previously known types.

The boron containing alloy is amenable to thermal treatment for themodification or improvement of various physical properties, such as,tensile strength and hardness. I have found, however, that thermaltreatment is not necessary nor desirable when the cast alloy is to beused for the majority of industrial applications.

The outstanding advantages of the present alloy are due, chiefly, to thefact that hardness and other physical properties are developed by thecombination of boron with one or more of the other essential components.Carbon is not essential in my alloy, but by reason of the fact thatvarying amounts of carbon are present in commercial grades of materialsused in producing the alloy I find that it is desirable to allow for theinclusion of a small percentage of carbon.

In order to obtain the maximum value of physical properties andcharacteristics it is important that the carbon content in the presentalloy does not exceed the theoretical ratio of the iron-carboneutectoid. By thus restricting the maximum amount of carbon theprecipitation of free car- The alloy of the present invention has a highdegree of we1dability,. that is, castings or other forms of the alloymay be surfaced or rebuilt to original dimensions with weld rods havingsubstantially the same composition, or materially differentcompositions. Bars, plates or other shapes of the alloy may be joined bywelding to fabricate parts of equipment, etc. By reason of the fact thatthe rate of cooling does not adversely affect the physical properties ofthe alloy, any suitable method of welding may be employed.

Examples of alloys within the scope of the present invention which Ihave found to be particularly valuable for wearing parts of equipmentare: manganese 9.50%, boron 0.65%, carbon 0.25%, and the balancesubstantially iron; manganese 12.50%, boron 0.95%, carbon 0.50%,,and thebalance substantially iron; manganese 15%, boron 1.10%, carbon 0.45%,and the balance substantially iron.

The alloy of the present invention comprises: manganese 6.25% to 16%,boron0.20% to 1.75%,

. carbon not exceeding a maximum of 0.85%, and

the balance substantially iron.

It will be understood that the alloy will contain fractional percentagesof impurities incidental to manufacture, such for example, as sulphurand phosphorus. Commercial grades of ferro-alloys and steel invariablycontain silicon, and consequently, varying amounts of silicon areintroduced into the present alloy as impurities incidental tomanufacture. The amount. of silicon in the alloy should not exceed 1%.

I claim:

An alloy characterized by relatively high resistance to deformation andabrasion containing manganese 6.25% to 16%, boron 0.20% to 1.75%, carbonnot exceeding a maximum of 0.85% and the balance iron.

ANTHONY G. DE GOLYER.

